Freenx resolution problem II

Dear all,

total newbie with Xfce but some experience with Linux and I'm facing a resolution problem with Freenx on my Xubuntu. Searching the forums I found this topic: http://forum.xfce.org/viewtopic.php?id=2657 but the links in there lead me nowhere and the last posting in the thread doesn't help because I do not have this path.However, I do have the same problem as described in that topic.

What I get is a window of 1280x1024 but inside of it is the desktop of the Xfce in the centre with a thick black frame surrounding it. However, the mouse is responsive even in the black frame and gives me e.g. the context menu of the right mouse button...